U.S. Pat. No. 8,792,826 B1 discloses a method for determining proximity between radio frequency devices and controlling switches using the analysis of a series of received signal strength indicator (RSSI) values. It further relates to a method for the control of a switch based on the proximity of the radio frequency devices. It is disclosed that the switch may be used to change the state of a door lock from locked to unlocked. Different so-called technical indicators are also disclosed that are used to determine the proximity.
However, the method disclosed in U.S. Pat. No. 8,792,826 may lead to a number of situations where the proximity of radio frequency devices to the switch will trigger a reaction although it was not the intention of the user. A car door may e.g. unintentionally be opened when a user passes in the vicinity of the car in a garage. Similarly, a door lock in an office space may e.g. unintentionally be opened when a user passes by his/her office in the corridor.
Thus, there is still room for improvements when it comes to providing a method for controlling access in a system comprising a portable device associated with a user and an access control device.